Effectiveness of oseltamivir in reducing COVID-19-related in-hospital deaths: A pharmacoepidemiological study

Oseltamivir, as a low-cost antiviral agent, may support or complement treatment of COVID-19. This study assessed whether oseltamivir is effective in reducing COVID-19 related mortality. This retrospective cohort study investigated real world data from a nationwide database of hospitalization due to severe acute respiratory syndrome in Brazil. We used propensity score matching to mimic a randomized controlled trial with "oseltamivir" and "no antivirals at all" as the intervention and control groups, respectively. A total of 21,480 and 268,486 patients admitted between February 2020 and January 2023 were included as intervention and control group respectively. After matching, the odds ratio (OR) of death was 0.901 (95% CI 0.873-0.930). For those who were admitted to the ICU, and on non-invasive and invasive ventilation, the OR of death were 0.868 (0.821-0.917,), 0.935 (0.893-0.980), and 0.883 (0.814-0.958), respectively. Overall, the use of oseltamivir was found to be associated with an attributable risk reduction of 2.50% (95% CI 1.77%-3.29%). Similar results were observed in those who were admitted to the ICU, and on non-invasive and invasive ventilation. Oseltamivir may offer a low-cost antiviral treatment for COVID-19.